lesson 1

• There are two types of reproduction: Asexual and sexual reproduction
• Asexual and sexual reproductions have advantages and disadvantages. What is important is through this life process, the continuity of life is assured
• Asexual reproduction


  Mode of reproduction that does not involve the use of gametes or sex cells
• Types of Asexual Reproduction

  • Fission
  • Fragmentation
  • Budding
  • Sporulation
  • Parthenogenesis
• Fission


  Type of asexual reproduction involving the division of the body into two or more equal parts
• Fission


  • paramecium
  • amoeba
• Fragmentation


  Type of asexual reproduction where the body breaks into two or more parts, with each fragment capable of becoming a complete individual
• Budding


  Type of asexual reproduction where a new individual arises as an outgrowth (bud) from its parent, develops organs like those of the parent, and then detaches itself
• Sporulation


  Type of asexual reproduction where new individual forms from an aggregation of cells surrounded by a resistant capsule or spore, which later on germinates
• Parthenogenesis


  A form of asexual reproduction by self-impregnation resulting in the production of a zygote from an unfertilized egg

  
• Parthenogenesis


  • scorpions, nematodes, mites, water fleas, wasps, some bees, and other insects
• Sexual reproduction


  Mode of reproduction that involves the use of gametes or sex cells
• Types of union of gametes

  • Conjugation
  • Isogamy
  • Heterogamy
• Conjugation


  A form of sexual reproduction in bacteria where two individual cells are united by a tube formed by outgrowths from one or both cells, and genetic material from one cell (designated the male) then passes through the tube to unite with genetic material in the other cell (designated female)
• Isogamy


  Fusion of similar gametes which are usually motile
• Heterogamy


  Fusion of dissimilar gametes, where a large immotile gamete (the egg) is fertilized by a small motile gamete (the sperm)

  
• Special terms used for Sexual reproduction

  • Bisexual reproduction
  • Hermaphrodite
• Bisexual reproduction


  Type of sexual reproduction involving the union of gametes from two genetically different parents
• Hermaphrodite


  An individual with both male and female reproductive tissues. In animals, "self-fertilization" is not common. In worms, a hermaphrodite needs a male to donate sperms in order to fertilize the oocytes in its body.
• Gametogenesis


  The process by which diploid precursor cells undergo meiotic division to become haploid gametes (sex cells)

  
• Gametogenesis in males (spermatogenesis)

  • Multiple mitotic divisions and cell growth of precursor germ cells
  • Two meiotic divisions (meiosis I and II) to produce haploid daughter cells
  • Differentiation of the haploid daughter cells to produce functional gametes (spermatozoa)

  
• Gametogenesis in females (oogenesis)


  • Formation of many primordial cells by mitosis during fetal development
  • Cell growth of oogonia until they are large enough to undergo meiosis (becoming primary oocytes)
  • Arrest of primary oocytes in prophase I until puberty
  • Completion of first meiotic division to form a secondary oocyte and a polar body
  • Arrest of secondary oocyte in metaphase II until fertilization
  • Completion of second meiotic division upon fertilization to form an ovum

  
• While the processes of spermatogenesis and oogenesis follow the same basic pathway, several key differences exist in the number of cells produced, size of cells produced, and timing of the process

  
• Fertilization


  A stage of development that results in a unicellular diploid zygote, which may occur externally (outside the body) or internally (inside the body)

  
• Cleavage


  A stage of development involving a series of mitotic divisions to produce a multicellular blastula from a unicellular zygote, where totipotent cells can differentiate to become any kind of cell

  
• Gastrulation


  A stage of development involving morphogenetic movements of the cells to produce a gastrula with distinct germ cell layers (ectoderm, endoderm, mesoderm)

  
• Organogenesis


  A stage of development where the different germ layers differentiate into specific organ systems

  
• Table 1 shows the fates of the cells of each germ layer in vertebrate animals

  
• Differentiation and Growth


  Growth is a stage of development characterized by an increase in the size of an individual, while development involves the formation of sex cells, zygote formation, and subsequent stages in one's life span, terminated by death

  
• Functions of the female reproductive system

  • Production of female sex cells
  • Reception of sperm cells from the male
  • Nurturing the development of and providing nourishment for, the new individual
• Female reproductive organs


  • Ovaries
  • Uterine tubes (fallopian tubes)
  • Uterus
  • Vagina
  • External genitalia
  • Mammary glands

  
• Ovaries


  Two ovaries each comparable to the size of an almond nut, suspended in the pelvic cavity and containing ovarian follicles with oocytes (female germ cells)
• Fallopian Tubes


  Extend from the ovaries to the uterus, with long, thin processes called fimbriae surrounding the opening, where fertilization usually occurs

  
• Uterus


  A pear-shaped organ with a larger rounded fundus, a body, and a narrower cervix that opens into the vagina
• Vagina


  The female organ for copulation, receiving the penis during intercourse and allowing menstrual flow and childbirth, with a hymen covering the opening in young females
• ed fimbriae


  Surround the opening of each uterine tube
• Fertilization


  Usually occurs in the part of the uterine tube near the ovary
• Uterus


  As big as a medium-sized pear, with a larger rounded part directed superiorly, the part superior to the entrance of the uterine tubes is called the fundus, the main part is called the body, and the narrower part is the cervix directed inferiorly

  
• Uterine cavity


  Continues through the cervix as the cervical canal, which opens into the vagina
• Vagina


  The female organ for copulation and functions to receive the penis during intercourse, allows menstrual flow and childbirth, extends from the uterus to the outside of the body